The present invention relates to a method of and a device for detecting torque, and more particularly to a method of and a device for detecting torque which are suitable for detecting torque under the condition of high-revolution speed or for detecting a very small torque.
A conventional method of and a device for detecting the torque of a torque-transmitting system is generally arranged such that an elastic member with a strain gauge attached thereto is inserted into the torque-transmitting shaft system, and a signal is put out via a slip ring as disclosed in, for instance, Japanese Patent Unexamined Publication No. 1940/1982. However, with such a method of and a device for detecting torque by using the slip ring, since a contacting point exists, noises become large owing to the occurrence of heat, etc. at the contacting point during high-velocity rotation, with the result that it is difficult to effect an accurate measurement.
As another kind of method of detecting torque in a non-contact state, a method of measuring a decline in the number of revolutions of the main shaft in a torque-transmitting shaft system due to the torque exerted thereto is discussed on pages 723 through 726 of a collection of treatises presented at a science lecture meeting for the 1984 autumn session of the Japan Society of Precision Engineering. This method is, however, applicable only to a low-rotation speed ranging between several thousand to 20,000 r.p.m. This is caused by the fact that a time lag from the time when a torque is applied to the main shaft until the time when the number of revolution of the main shaft is actually reduced is large, so that there is a problem in this method that the response characteristics is unsatisfactory.